Detailed Modeling of Channelized Deposits Using a Process-Based Stochastic Approach

Cojan, Isabelle¹, Jacques Rivoirard¹, François Geffroy¹ (1) Ecole des Mines de Paris, Fontainebleau, France

Process-based stochastic models offer the possibility to represent in a realistic manner the geometries and arrangements of complex deposits. This is in particular the case of the channelized deposits associated to meandering systems, whether fluvial or turbiditic.

In the fluvial model, the architecture of the system is essentially controlled by migration, avulsion and aggradation, which rule the deposition of the sedimentary bodies and their facies (point bar, mud plug, overbank deposits, levee/crevasse splay …). These factors control, in particular, the development and connectivity of point bars. In more details, the grain size distribution of point bars depends on the sedimentary load of overbank flows, which can vary in time, and on the vertical sorting.

While the scale is dramatically different, submarine meandering channels present a marked similarity with the terrestrial rivers, in particular with regard to their 2D morphology, as was pointed by many authors. The sedimentary load, however, is the governing factor of turbidity currents. Based on this, a model of channelized turbiditic reservoirs is developed, that includes a varying sediment load through time and space, and a mass balance, taking into account the initial (upstream) grain size composition of the turbiditic flow and its (more or less depositional or erosive) nature. Different channelized deposits (lateral accretion package, coarse channel lag, fine channel fill) can thus be modeled, with individualized grain size distribution.